KIEV/SIMFEROPOL, Ukraine, March 15 (Reuters) - Pro-Russian leaders in Crimea made final preparations on Saturday for a referendum widely expected to transfer control of the Black Sea region from Ukraine to Moscow, despite an outcry and threat of sanctions from the West.

Russia vetoed a United Nations Security Council resolution that declared the referendum invalid, as Ukraine's defence ministry said it scrambled aircraft and paratroops to confront a Russian encroachment beyond Crimea's regional boundary.

Ukraine's new rulers accused "Kremlin agents" of fomenting deadly violence in the Russian-speaking east and urged people not to respond to provocations Kiev fears Moscow may use to justify further incursions its takeover of Crimea. Russia issued a new statement saying it was ready to protect Ukrainians from nationalist militants it said were threatening eastern cities.

Sunday's vote in Crimea, dismissed by Kiev and Western governments as illegal, has triggered the worst East-West crisis since the Cold War and marks a new peak in turmoil in Ukraine that goes back to November when now ousted President Viktor Yanukovich walked out on a trade deal with the European Union.

Though the situation was calm on the Black Sea peninsula itself on Saturday ahead of the vote, tensions remained high in eastern Ukraine where two people were killed in Kharkiv late on Friday.

Crimean Prime Minister Sergei Aksyonov, whose election in a closed session of the regional parliament is not recognised by Kiev, said there were enough security personnel to ensure the poll would be safe.

"I think we have enough people - more than 10,000 in the self-defence forces, more than 5,000 in different units of the Interior Ministry and the security services of the Crimean Republic," he told reporters.

In Kiev, the Ukrainian parliament voted to dissolve the Crimean regional assembly which has organised the referendum and backs union with Russia.

And on Kiev's Independence Square or Maidan - lodestar of the revolt against the Moscow-backed Yanukovich - hundreds of people chanted "Crimea is Ukraine! Crimeans, we support you!"

One Ukrainian nationalist leader in the Kiev legislature said the Crimean assembly must be sanctioned to discourage separatist movements in the mainly Russian-speaking east.

Aksyonov and Moscow do not officially recognise that Russian troops have taken control of Crimea, and say that thousands of unidentified armed men visible across the region belong to "self-defence" groups created to ensure stability.

But the Russian military has done little to hide the arrival of thousands of soldiers, along with trucks, armoured vehicles and artillery. Masked gunmen surrounding Ukrainian military bases in Crimea have identified themselves as Russian troops.

"REAL DANGER" OF INVASION

Moscow leases the Crimean port of Sevastopol from Kiev to station its Black Sea Fleet. Under the deal it can station up to 25,000 troops there but there movements are restricted onshore.

Polling stations will open at 8 a.m. (0600 GMT) on Sunday and close 12 hours later. Preliminary results are expected within hours of polls closing on Sunday night.

Crimea's electorate of 1.5 million, according to a format of the ballot paper issued last week, will choose between one of two options - but both imply Russian control of the peninsula.

Many of the ethnic Russians who have a majority on the peninsula seem likely to back the first option on the ballot, union with Russia, if only for economic reasons. A second option is independence, initially within Ukraine, that Crimea's new leaders say they will use as a basis for accepting Russian rule.

Ethnic Tatars, Sunni Muslims of Turkic origin who make up 12 percent of Crimea's population, have said they will boycott the referendum, despite promises by the authorities to give them financial aid and proper land rights.

Acting Ukrainian president Oleksander Turchinov referred to three deaths in two days in two eastern cities - Donetsk and Kharkiv - and said there was "a real danger" of invasion by Russian troops across Ukraine's eastern border.

Populations of both cities have large numbers of Russian- speakers, significant since Russian President Vladimir Putin has vowed to protect ethnic Russians and Russian-speakers in Ukraine. His foreign ministry said on Saturday it would consider requests from people in Ukraine for protection - similar language to that used to justify Moscow's move in Crimea.

Addressing members of Yanukovich's party, Turchinov said: "You know as well as we do who is organising mass protests in eastern Ukraine - it is Kremlin agents who are organising and funding them, who are causing people to be murdered."

Two men, described by police as pro-Russian demonstrators, were shot dead in a fight in Kharkiv late on Friday. A Ukrainian nationalist was stabbed to death when pro-Russia and pro-Ukraine demonstrators clashed in Donetsk on Thursday.

Turchinov, quoted by local media, closed the parliamentary session by saying: "The situation is very dangerous. I'm not exaggerating. There is a real danger from threats of invasion of Ukrainian territory and we will reconvene on Monday at 10."

DEFENDING "COMPATRIOTS"

Russia has refused to recognise the new Western-backed interim administration in Kiev. Its foreign ministry unnerved the new authorities in Kiev by saying clashes in Donetsk showed Ukrainians had lost control of the situation there.

Ukraine's interior minister accused ousted president Viktor Yanukovich of promoting unrest with "extremist Russian forces". Arsen Avakov issued an appeal on Facebook: "Don't let them manipulate you! Stop this hysteria ... This isn't a game of toy soldiers - this is a real conflict and people's real lives."

Two men, aged 21 and 30, were killed in Kharkiv by buckshot late on Friday when pro-Russian demonstrators besieged an office of the far-right Ukrainian nationalist group Right Sector, which rose to prominence fighting riot police in Kiev over the winter.

Police said 32 Right Sector activists and six pro-Russian demonstrators were detained and a number of weapons seized.

Kharkiv governor Ihor Baluta, newly appointed by the interim authorities in Kiev, said the "well-planned provocation by pro-Russian activists" began when unidentified men in a minibus provoked a confrontation with pro-Russia demonstrators and then drove off. When pursuing demonstrators caught up with the vehicle, it was parked outside the nationalists' building.

The Right Sector spokesman, quoted by Interfax-Ukraine news agency, said his group had taken no part in the initial clash and believed the minibus was left outside its office by others.

The Russian Foreign Ministry said it had information that armed Right Sector militants were opening an "eastern front" and planning to reinforce their activists in eastern cities.

Western powers, preparing economic sanctions against Russia over Crimea, largely dismiss Russia's characterisation of the new authorities in Kiev as the successors of Nazi-allied Ukrainian forces which fought the Red Army in World War Two.

Authorities in Kharkiv banned political gatherings that were planned in the city over the weekend. In Donetsk, hundreds of people rallied in Lenin Square, flying Russian flags and calling for a referendum in the region similar to that in Crimea.

In Moscow, a large crowd estimated by witnesses at some 30,000 demonstrated against Russia's action in Ukraine, the biggest protest against Putin in two years. At a smaller rally, people chanted "Crimea is Russia!" and "No to fascism!"

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